Process and apparatus for cleaning furnace gases



United States Patent lnventor Robert Katz Woodmere, New York Appl. No.730,851 v Filed May 21, 1968 Patented Aug. 25, 1970 Assignee Scrubaire,Inc.

Forest Hills, New York a corporation of New York PROCESS AND APPARATUSFOR CLEANING FURNACE GASES 12 Claims, 1 Drawing Fig.

US. Cl 110/18, 1 10/ 1 19 Int. Cl F23g 3/00, F23j 15/00 Field of Search1 10/8, 8A,

llb

Primary Examiner- Kenneth W. Sprague Att0rney Joseph l-lirschmannABSTRACT: Furnace flue gases, and particularly incinerator flue gases ofapartment houses wherein the same chimney or stack, provided with adamper, serves for discharging the furnace combustion gases and forreceiving garbage at the different levels, are withdrawn from the stackin advance of the damper and subjected to a plurality of stages ofscrubbing with water of different degrees of purity, and then returnedto the stack by means of a fan or blower at a point above the damper,the damper being cooled with fresh water to prevent ignition of garbagedeposited thereon either during or between combustion cycles, suchcooling water being employed in the last gas-scrubbing stage.

MAKE-UP W 2 CLEAN ATER RECIRCULATING WATER UN: 31

Patented Aug. 25, 1970 INVENTOR. Robert Katz ATTORNEY.

PROCESS AND APPARATUS FOR CLEANING FURNACE GASES The present inventionrelates to an improved process and apparatus for cleaning furnace fluegases and particularly incinerator flue gases of solid and gaseouspollutants.

In accordance with the present invention, the flue gases entering achimney or smokestack in advance of the damper are bypassed into ascrubber system which removes the suspended particles and the cleanedgases are then returned to the chimney or smokestack at the dischargeside of the damper.

As the invention is of particular value in the cleaning of the fluegases of apartment house incinerators, it will be further described indetail hereinbelow in connection with such use, but it will be readilyapparent that the invention is applicable also to commercialinstallations for the removal of soot and other suspended particles andsoluble gases from flue gases.

It is the general object of the invention to provide an improved processand apparatus for scrubbing and cleaning flue gases which can beincorporated in existing buildings or in buildings in process ofconstruction.

It is also an object of the invention to provide an improved process andapparatus for the cleaning of incinerator and furnace flue gases withthe aid of water in which the water is utilized economically and with aminimum expenditure thereof.

It is a further object of the invention to provide a process andapparatus for the cleaning of incinerator and furnace flue gases whereinthe latter are subjected to repeated treatment with water, both re-usedand fresh water, whereby a high degree of purification is attained.

it is a still further object of the invention to provide a cooled damperin a chimney or smokestack of apartment houses wherein the same stack isused for the furnace of the apartment house as well as for the disposalof garbage through chutes at the different floor levels, the damperserving to block off the stack so that combustion gases may be divertedfrom a point in advance of the damper to the scrubber section of theapparatus, the cleansed gases being returned to the stack at the otherside of the damper; the damper being constructed so as to be capable ofbeing cooled with water to guard against ignition of rubbish and garbagethat may be discharged thereon and thereby prevent pollution of thegases which have been cleaned in the scrubber section of my improvedapparatus and returned to the stack.

Another object of the invention is to provide an apparatus of the kindindicated wherein the cooling water for the damper is utilized asmake-up water for the scrubber section.

Other objects and advantages of the invention will appear from thefollowing detailed description thereof and the features of novelty willbe set forth in the appended claims.

The accompanying drawing shows schematically a furnace and smokestackarrangement provided with my improved cooled damper and with connectionsfor bypassing the furnace gases to the scrubber system and with a returnconnection for discharging the cleaned gases into the chimney or stackabove the damper.

Referring to the drawing, the chimney or stack is shown at 10, therebeing provided a damper 11 which, when closed, blocks the flow offurnace gases through the stack, the furnace being indicateddiagrammatically at 12. At the various floors of the apartment housethere are provided garbage chutes, indicated diagrammatically at 13, andwhen the furnace is not in operation, the damper 11 is open so that thegarbage falls freely into the furnace before the furnace is fired again.I g a g Combustion of'the garba eaccur iriih fuiriace 12 and th furnacegases are normally discharged through the stack 10. The furnace gasesare usually soot and smoke-laden, by reason of the fact that the garbageis generally moist and does not burn readily; and in addition, the gaseshave suspended therein more or less large particles of burnt paper, sothat the discharged gases contribute to an important degree to thepollution of the city atmosphere.

In accordance with the present invention, the flue gases are by-passedto a scrubber system (by closing damper 11) wherein the suspended matteris substantially completely removed along with water-soluble noxiousgases, such as the sulfur oxides, nitrogen oxides, and the like, andthereafter the gases are discharged in cleansed condition into thesmokestack at a point above the damper 11. To this end, the

gases are withdrawn from the smokestack by the conduit 14 and flow intoa scrubber apparatus having three sections comprising a venturi spraysection, a tray section using either bubble caps, sieve trays or thelike, and a polishing section using sprays of clean water which arecollected and charged 'into the tray section.

It will be understood that when the scrubber section is in operation,the damper is in the closed or gas-blocking position.

The soot-laden gases are directed from the furnace section 12 andthrough the pipe 14 into the chamber 15 of the scrubber 16. In thescrubber, the gases are first preliminarily washed by a water spray 17as they pass through a venturi throat 18 and into the chamber 19. Thegases are still under suction as they enter the chamber 19, but are at arelative super-pressure with respect to region 19a, which is under themaximum suction created by a fan or blower 27. In the preferred form ofthe apparatus, the gases pass through a multitude of small openings 20in a tray 21 which supports a layer or bed of water 22, the differencein pressure between the spaces 19 and being sufficient to enable thegases to bubble through the layer of water 22. As they pass through thewater layer,'they are further scrubbed of a large part of their solidmatter and as they escape above the layer of water, as indicated by thearrows 22, they pass into the discharge conduit 24 where they meet aspray of clean water 23 and receive a final cleansing.

From the conduit 24 they are discharged into the smokestack above thedamper as indicated in the drawing.

As will be seen from the foregoing, the polluted gases are subjected toan initial cleaning at the throat 18, then given a more thoroughcleansing in the layer of water 22, and finally by the spray 23.

Upon discharge from the conduit 24, they are substantially completelyfree of solid matter and also of the gases which are soluble in water.

As stated hereinbefore, the damper of the smokestack is water-cooled inorder to prevent ignition of garbage or rubbish deposited thereon whentenants throw such material down the chutes while the damper is inclosed position and still hot from the preceding combustion cycle, orwhile the damper is in closed position during operation of theincinerator furnace to enable the combustion gases temporarily to bypassthe smokestack. This clean damper cooling water constitutes, inaccordance with the invention, at least part of the spray 23, and tosuch cooling water there may be added fresh make-up water which replaceswater lost by evaporation and in the form of suspended droplets in thegases discharged at 24.

The fresh water is charged into the damper through a pipe 25 and iscompelled to travel the full length of the damper by a baffle 11a or inany other suitable manner, and is discharged through a pipe 26 which isconnected to the spray nozzle 23a and forms part of the spray 23. Thedamper is operated in known manner by an actuator 11b of any suitabletype.

The overflow from the tray 21 falls into a tank or sump 28 from whichwater is withdrawn by a pipe 29 and charged by the pump 30 into conduit31 which feeds the water to the spray nozzle 32 at the venturi sectionof the scrubber. The overflow from the sump 28 carrying the lighterparticles of soot is discharged through a pipe 33 and may be dischargedas waste water, or, when the supply of water is limited, it may bedirected into a settling tank, from which the at least partiallyclarified water can be fed to the nozzle 32 or onto the tray 21. Thesump 28 can be provided with a cleaning out valve 34 for discharging orflushing out soot deposited at the bottom of the sump.

It will be understood that the perforated tray 21 represents only onetype of device for effecting a partial cleansing of the gases. The traycan be replaced by bubble caps or by a separate spray system.

lclaim'.

1. Process for cleaning furnace flue gases which are discharged througha smokestack provided with a damper, which comprises keeping the damperclosed and by-passing the furnace flue gases into a scrubber system,scrubbing the gases in said system by separate bodies of water, andthereafter returning the cleaned gases to the smokestack of the furnaceat a point above the damper.

2. Process according to claim 1, wherein clean water is charged into thedamper of the Smokestack to cool the same and thereafter charging suchwater into the scrubber for the final scrubbing of the gases.

3. Process according to claim 1, wherein the scrubbing of the gasesincludes the steps of increasing the speed of the flue gases andsubjecting them to a first water spray, then causing the gases to bubblethrough a layer of water, and finally subjecting the gases to a spray offresh water, directing said lastmentioned spray into a said layer.combining the overflow of said layer with the discharged water of saidfirst spray, drawing off the soot-laden upper portion of the so-formedbody of water, and utilizing the lower portion of such body of water toform the first spray.

4. in combination with a furnace and stack thereof provided with adamper, of means for scrubbing the furnace gases and returning them tothe stack above the damper, comprising a conduit for withdrawing thegases from beneath the damper and a scrubber system into which theconduit discharges the soot-laden gases and comprising a water-spraysection in which the gases are first subjected to a water spray. asecond scrubbing section comprising means for subjecting the gases tothe cleansing action of a further body of water, a further spraysection, and means for charging clean water into the latter, and a fanfor withdrawing the gases from the scrubber section and charging thesame into the smokestack at a point above the damper.

5. Flue gas cleaning apparatus according to claim 4, wherein the damperis hollow and is provided with an inlet and an outlet for cooling water,and a conduit for leading the discharged water into the scrubber.

6. Apparatus according to claim 5, wherein the damper cooling water isbrought into contact with the flue gases in the last cleaning step ofthe scrubber.

7. Apparatus according to claim 4, wherein the cleaning water of thesecond scrubbing stage is collected and recirculated and discharged intothe first scrubbing stage.

8. Apparatus according to claim 4, wherein the second scrubbing stagecomprises a perforated tray on which is disposed a layer of water, and ablower arranged to produce sufficiently low sub-atmospheric pressure tocause the flue gases to flow through the perforations of the tray andbubble through the layer of water.

9. Apparatus according to claim 8, wherein the tray is arranged toreceive the cleaning water discharging from a subsequent cleaning stageof the scrubber.

10. Apparatus according to claim 9, including means for collecting theoverflow from said tray, and means for pumping the water from saidcollecting means to the first cleaning stage of the scrubber.

11. The combination with the stack of an apartment house garbageincinerator provided with chutes at the different floors discharginginto the stack, said stack having a damper therein, of a multistagescrubber unit, a conduit connected with the stack below the damper fordischarging into the scrubber unit the flue gases issuing from thefurnace of the in cinerator, said scrubber including a final stagewherein the gases are brought into contact with clean water, a stagewherein they are brought into contact with water discharged by said laststage, and a conduit for returning the cleaned gases to the stack abovethe damper.

12. The combination according to claim 11, wherever the damper ishollow, and including feed and discharge conduits for bringing the freshwater first into heat-exchange relation with the damper to cool itsufficiently to prevent ignition of garbage falling upon it.

